diff --git a/scripts/download-using-manifests.pl.in b/scripts/download-using-manifests.pl.in
index 751452526..382eb7c3a 100644
--- a/scripts/download-using-manifests.pl.in
+++ b/scripts/download-using-manifests.pl.in
@@ -9,6 +9,7 @@ my $logFile = "@localstatedir@/log/nix/downloads";
 
 open LOGFILE, ">>$logFile" or die "cannot open log file $logFile";
 
+delete $ENV{"NIX_ROOT"};
 
 # Create a temporary directory.
 my $tmpDir;
diff --git a/scripts/nix-prefetch-url.in b/scripts/nix-prefetch-url.in
index 5f6ea4c0d..7d0a17163 100644
--- a/scripts/nix-prefetch-url.in
+++ b/scripts/nix-prefetch-url.in
@@ -3,6 +3,9 @@
 url=$1
 expHash=$2
 
+# to prevent doing more than 1 chroot
+unset NIX_ROOT
+
 hashType=$NIX_HASH_ALGO
 if test -z "$hashType"; then
     hashType=md5